Purification of metals from mixtures thereof

Abstract

A process for preparing a pure PGM (platinum group metal) from a material containing a plurality of PGM compounds, wherein the PGM is selected from the group consisting of Pt, Pd, Os, Ir, Ru, Rh and Re, and the process includes initially forming the PGM in activated form by reduction of PGM ions in aqueous solution at pH 6-8 by a reducing agent, preferably, hydrogen. Subsequently, the activated PGMs are treated by (a) reacting the material with a gaseous reactant to produce a gaseous mixture comprising at least a first volatile PGM complex having a first decomposition temperature and a second volatile PGM complex having a second decomposition temperature, the first decomposition temperature being lower than second decomposition temperature, and a first residue; (b) separating the gaseous mixture from the first residue; (c) heating the gaseous mixture to the first decomposition temperature to produce a pure first PGM and a first volatile PGM complex-free gaseous mixture; (d) collecting the pure first PGM; (e) heating the first volatile PGM complex-free gaseous mixture to said second decomposition temperature to produce a pure second PGM and a second gaseous mixture; (f) and collecting the pure second PGM. The process provides for the extraction and separation of PGMs in an efficacious, economic and environmentally safe manner from ores, slag, mattes and slurries.

Description

[0001] This invention relates to a process of purification of metals from mixtures and compounds thereof, particularly, the extraction and separation of individual metals of the group defined herein as the platinum group of metals (PGMs) from materials comprising the metals, such as ore, slag, scrap, slurry concentrate, metallurgical intermediates, by-products and the like by the formation, separation and decomposition of volatile compounds comprising the metals. The invention further relates to a method for the production of particulate activated PGMs of use in the aforesaid purification process.BACKGROUND TO THE INVENTION[0002] By the term "platinum group metal" (PGM) as used in this specification and claims is meant a metal selected from the group consisting of platinum, palladium, rhodium, osmium, ruthenium, iridium and rhenium.[0003] Each of these PGMs is known to form volatile compounds of at least one of the three following groups.[0004] 1. A first group of PGM volatile compo...

AI Technical Summary

Benefits of technology

"The patent is about a process for purifying metals from mixtures containing them, particularly the platinum group metals, by using a process called thermal decomposition. The process involves the formation, separation, and decomposition of volatile compounds of the metals. The patent also describes the properties and synthesis of these compounds. The technical effect of the patent is to provide a more efficient and effective way to purify these metals from their mixtures."

Problems solved by technology

Others are known to be difficult to synthesis or have extremely high temperatures of decomposition of the order of 600.degree. C.

However, a difficulty with the use of these complexes for metal extraction and separation, is the unfavourable selectivity of the synthesis, as well as the similar sublimation temperatures of the diketonates.

The distinct exception is the trifluorophosphine complex of palladium which has a low thermal stability.

Although, volatile individual PGM compounds and complexes as hereinbefore described are known to be formed and decomposed thermally to produce the pure metal, it is not known whether such processes are applicable when a plurality of PGMs are present together in varying degrees as various compounds, in such materials as, for example, ore, slag, scrap, slurry, concentrate, metallic intermediates, by-products and the like.

It is known, however, that PGMs do not always react with an aforesaid gaseous reactant to a sufficient extent in a satisfactory manner.

However, todate, the present PGM extraction processes suffer from being relatively expensive.

The results show that inefficient reaction occurred.

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